Observations of resuspended diatoms in the turbid tidal edge     

Cathy H. Lucas 《Journal of Sea Research》2003,50(4):301-308

Observations of resuspended diatoms in the shallow waters (<60 cm) of the turbid tidal edge are described for single sites on two tidal flats–the Molenplaat in the Westerschelde estuary, and the Hond in the Ems-Dollard estuary, The Netherlands. High concentrations of chlorophyll-a (chl-a) were observed in the trailing edge of the ebbing tide in water depths of <20 cm, after which concentrations decreased markedly. Peak mean values were 19 μg chl-a l⁻¹ in 10 cm of water at the Molenplaat, and 45 μg chl-a l⁻¹ in 5 cm of water at the Hond. Similar trends were observed on the flooding tide, although peak values were far less pronounced (6 and 30 μg chl-a l⁻¹ respectively). Microscopic examination of the diatom community within the turbid tidal edge at the Molenplaat revealed that peaks in biomass were caused by suspended benthic diatoms, as well as the large centric diatom Coscinodiscus sp., particularly on the ebb tide. Planktonic diatoms other than Coscinodiscus sp. were more randomly distributed and did not appear to follow any particular trend. It would seem that as the tide recedes, resuspended benthic diatoms and large Coscinodiscus sp. cells become concentrated in the shallow water. However, the virtual absence of Coscinodiscus sp. from the leading edge of the flooding tide suggests that most of the resuspended cells do not settle to the seabed, but are washed away into the channels. The small peak of benthic diatoms at the leading edge of the flood tide is most likely resuspended locally from the sediment, along with large numbers of diatom frustules.  相似文献   

Using Topological Relationships to Inform a Data Integration Process   总被引：2，自引：0，他引：2  

Sue Hope  Allison Kealy 《Transactions in GIS》2008,12(2):267-283

When spatial datasets are overlaid, corresponding features do not always coincide. This may be a result of the datasets having differing quality characteristics, being captured at different scales or perhaps being in different projections or datums. Data integration methods have been developed to bring such datasets into alignment. Although these methods attempt to maintain topological relationships within each dataset, spatial relationships between features in different datasets are generally not considered. The preservation of inter‐dataset topology is a research area of considerable current interest. This research addresses the preservation of topology within a data integration process. It describes the functional models established to represent a number of spatial relationships as observation equations. These are used to provide additional information concerning the relative positions of features. Since many topological relationships are best modelled as inequalities, an algorithm is developed to accommodate such relationships. The method, based on least squares with inequalities (LSI), is tested on simulated and real datasets. Results are presented to illustrate the optimal positioning solutions determined using all of the available information. In addition, updated quality parameters are provided at the level of the individual coordinate, enabling communication of local variation in the resultant quality of the integrated datasets.  相似文献   

THE NEGOTIATION OF SPACE AMONG SEX WORKERS IN CEBU CITY, THE PHILIPPINES     

Cathy McIlwaine 《Singapore journal of tropical geography》1997,17(2):150-164

The paper examines the experiences of space among sex workers in Cebu City, a major service and commercial centre in the Visayan region of the Philippines. It explores the issue of space from a number of perspectives and scales: first, at the national level in terms of migration patterns among sex workers; second, at the local level in relation to how sex workers experience and construct urban spaces through residence and working patterns; and finally, from a community perspective, the nature of domestic spaces among these women. The underlying theme of the paper centres around the contradictory ways in which social opprobrium is often reflected in spatial seclusion among sex workers. On the one hand, they are constrained in their experiences of space. On the other, the construction of their own particular spaces reflects a high degree of resourcefulness and resistance. This is corroborated further by the fact that involvement in the sex industry creates a different set of spatial aspirations and awareness among sex workers compared with those of the wider population.  相似文献   

Interaction of the recent 50 year SST trend and La Niña 2010: amplification of the Southern Annular Mode and Australian springtime rainfall     

Eun-Pa Lim  Harry H. Hendon  Julie M. Arblaster  Christine Chung  Aurel F. Moise  Pandora Hope  Griffith Young  Mei Zhao 《Climate Dynamics》2016,47(7-8):2273-2291

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Late Pleistocene glaciation of the Mt Giluwe volcano,Papua New Guinea     

Timothy T. Barrows  Geoffrey S. Hope  Michael L. Prentice  L. Keith Fifield  Stephen G. Tims 《Quaternary Science Reviews》2011,30(19-20):2676-2689

The Mt Giluwe shield volcano was the largest area glaciated in Papua New Guinea during the Pleistocene. Despite minimal cooling of the sea surface during the last glacial maximum, glaciers reached elevations as low as 3200 m. To investigate changes in the extent of ice through time we have re-mapped evidence for glaciation on the southwest flank of Mt Giluwe. We find that an ice cap has formed on the flanks of the mountain on at least three, and probably four, separate occasions. To constrain the ages of these glaciations we present 39 new cosmogenic ³⁶Cl exposure ages complemented by new radiocarbon dates. Direct dating of the moraines identifies that the maximum extent of glaciation on the mountain was not during the last glacial maximum as previously thought. In conjunction with existing potassium/argon and radiocarbon dating, we recognise four distinct glacial periods between 293–306 ka (Gogon Glaciation), 136–158 ka (Mengane Glaciation), centred at 62 ka (Komia Glaciation) and from >20.3–11.5 ka (Tongo Glaciation). The temperature difference relative to the present during the Tongo Glaciation is likely to be of the order of at least 5 °C which is a minimum difference for the previous glaciations. During the Tongo Glaciation, ice was briefly at its maximum for less than 1000 years, but stayed near maximum levels for nearly 4000 years, until about 15.4 ka. Over the next 4000 years there was more rapid retreat with ice free conditions by the early Holocene.  相似文献   

A study of objective methods for water mass analysis,applied to the Iceland Basin     

de Boer  Cathy J.  van Aken  Hendrik M. 《Ocean Dynamics》1995,47(1):5-22

Ocean Dynamics - Cluster analysis and principal component analysis have been applied to multi-parameter hydrographic data from the Iceland Basin. The results indicate that both objective methods...  相似文献   

Shifts in the synoptic systems influencing southwest Western Australia   总被引：1，自引：1，他引：1  

Pandora K. Hope  Wasyl Drosdowsky  Neville Nicholls 《Climate Dynamics》2006,26(7-8):751-764

A self-organising map is used to classify the winter circulation affecting southwest Western Australia (SWWA) into 20 different synoptic types. The changes in the frequency of these types and their links to observed rainfall are analysed to further understand the significant, prolonged, rainfall drop observed in this region since 1975. The temporal variability of the different synoptic types link well with the observed rainfall changes. The frequency of the troughs associated with wet conditions across SWWA has declined markedly since 1975 while the frequency of the synoptic types with high pressure over the continent, associated with dry conditions, has increased. Combining the frequency of the synoptic systems with the amount of observed rainfall allows a quantitative analysis of the rainfall decline. The decreased frequency of the troughs associated with very wet conditions accounts for half of the decline. Reductions in the amount of rainfall precipitating from each system also contribute to the decline. Large-scale circulation changes, including increases in the mean sea-level pressure and a decrease in the general baroclinicity of the region have been associated with the rainfall decline. These changes are suggested to be linked to increasing levels of greenhouse gases. Due to the strong link between the number of trough types and the rainfall over SWWA, the shifts in the frequency of these synoptic types could be used as a tool to assess simulated rainfall changes, particularly into the future.  相似文献   

Some economics of ‘dangerous’ climate change: Reflections on the Stern Review     

Simon Dietz  Chris Hope  Nicola Patmore 《Global Environmental Change》2007,17(3-4):311-325

The Stern Review on the Economics of Climate Change concluded that there can be “no doubt” the economic risks of business-as-usual (BAU) climate change are “very severe” [Stern, 2006. The Economics of Climate Change. HM Treasury, London, p. 188]. The total cost of climate change was estimated to be equivalent to a one-off, permanent 5–20% loss in global mean per-capita consumption today. And the marginal damage cost of a tonne of carbon emitted today was estimated to be around $312 [p. 344]. Both of these estimates are higher than most reported in the previous literature. Subsequently, a number of critiques have appeared, arguing that discounting is the principal explanation for this discrepancy. Discounting is important, but in this paper we emphasise that how one approaches the economics of risk and uncertainty, and how one attempts to model the very closely related issue of low-probability/high-damage scenarios (which we connect to the recent discussion of ‘dangerous’ climate change), can matter just as much. We demonstrate these arguments empirically, using the same models applied in the Stern Review. Together, the issues of risk and uncertainty on the one hand, and ‘dangerous’ climate change on the other, raise very strongly questions about the limits of a welfare-economic approach, where the loss of natural capital might be irreversible and impossible to compensate. Thus we also critically reflect on the state-of-the-art in integrated assessment modelling. There will always be an imperative to carry out integrated assessment modelling, bringing together scientific ‘fact’ and value judgement systematically. But we agree with those cautioning against a literal interpretation of current estimates. Ironically, the Stern Review is one of those voices. A fixation with cost-benefit analysis misses the point that arguments for stabilisation should, and are, built on broader foundations.  相似文献   

Geoecology of ecosystem recovery at an inactive coal mine site,New Zealand     

Cathy G. Rufaut  Dave Craw 《Environmental Earth Sciences》2010,60(7):1425-1437

Ecological restoration of the Wangaloa coal mine in southern New Zealand is hindered by a range of geoecological factors. The site has some substrate acidification (down to pH 1) and acid rock drainage with discharge waters initially down to pH 4, although this has since risen to ca. pH 6. Surface and ground waters develop elevated sulfate (up to 700 mg/kg) during oxidation of pyrite in coal and quartz in waste rock. Coal has elevated boron content (up to 450 mg/kg) and surface waters on coal-rich waste rock have up to 6 mg/L dissolved boron. Evaporation causes formation of salt encrustations dominated by gypsum with minor boron salts. Boron is bioavailable and may be at toxic levels (>200 mg/kg) in some plants. Quartz-rich waste rock is readily eroded, and develops a cm-scale low-nutrient quartz pebble armouring layer with low water retention properties. All waste rocks including loess siltstone have low nutrient contents, and low moisture retention properties, that are barely sufficient for plant establishment. Native plants introduced to the site during rehabilitation have grown on loess substrate (up to fivefold increase in height over 3 years), with poor or no growth on coal-rich and quartz-rich substrates. In contrast, natural colonisation of manuka (Leptospermum scoparium) has been most effective at revegetation on even the most hostile substrates. This natural revegetation has been facilitated by islands of manuka established accidentally during 60 years of mining history. Manuka from local genetic stock is most viable for this revegetation, and introduced manuka seedlings have had a 70% mortality rate. Natural plant colonisation is the key step in overall ecosystem recovery, and invertebrates rapidly colonise beneath new shrubs irrespective of the nature of the substrate from vegetation islands that have high invertebrate numbers and species richness.  相似文献   

Use of the Stinkbug,Encosternum delegorguei (Hemiptera,Tessaratomidae), for Food and Income in South Africa     

Cathy M. Dzerefos  Ed T. F. Witkowski  Rob Toms 《社会与自然资源》2014,27(8):882-897

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